Method of preventing decomposition of bicarbonates in solution



[Jet 23, 1928. 1,689,059

J. A. SHAW METHOD OF PREVENTING DECOMPOSITION OF BICARBONATES IN SOLUTION Filed Oct. 5 1925 INVENTOR BY $3. M

PM) ms ATTORNEYS Patented Get. 2 l zfifl lessens JOSEPH ALLAN SHAW, OI? PITTS BURGH, PET.

SYLV&NIA, ASSEGNGR TC THE KOPPEES MEIHGD 0F PREVENTIEIG DECQMPQSITION OF BICARBQNATES IN SQLUTIO'N.

Application filed Qctober 3, 1325.

This invention relates to a method of preventing the decomposition of hicarhonates such calcium bicarbonate, in solution, and is particularly valuable in large scale apparatus such as the primary gas coolers of coal gas plants, although the invention has many other applications.

In apparatus of this character Where it necessary to employ cooling agent waters which are known temporarily hardl that is, lhose containing varying amounts of calcium bicarbonate, it is found that upon heating of the solution carbon dioxide gas esrfapcs until the vapor pres sure in the atmosphere above the solution is built up and calcium hicarbonato decomposes until the deficiency CO concentration in. the solution. is made upaccording to the following reaction:

Ca (HG J 2 CaCO CO +H O The highly insoluble Ca f/() separates out from the solution and is deposited as scale. This scale is a source of greatannoyance in such apparatus as gas coolers:

where the water tubes become encrusted with the scale and require frequent cleaning in order to get ellicient results out of the apparatus.

I provide for artificially holding the C6 in solution. This may be done in several ways as, for example, by covering the solution with a liquid of low vapor pressure, such as a thick mineral oil. This coating of oil largely prevents the escape of CS or at least retards it to a great extent thus preventing the deconioosition of calcium bicarbonate according to the above reaction, or any reaction involving the loss of CO as long as the evolution. of CO is not violent or accompanied by boiling or the like. The use of an oil film or layer is also desirable in that it prevents evaporation or steaming of the solution so long as the boil-- ing point is not reached, and this of pen ticular value Where the apparatus is located Within a building or other enciosin'e having any steel or iron work. The use oi the oil 'layer materially reduces the tendency to rust, which is ordinarily present,

The accompanying figure of drawing which illustrates a preferred embodiment oi the invention as applied to gas cocien shows a sicle elevation, partly broken away,

Serial No. 358.

or s primary gas cooler embodying my invention.

l'n illustrated embodiment of the invcntion. there shown it cooler consisting of a verti al shell 1 which is divided into five compartments 2, 3 t, 5 and 5 by hori zontal tube sheets 3 and '2' and a vertical baffle 8. The compartment 2, which that portion of the cooler space above the tube sheet ii, is open to the atmosphere. The compartments 3 end 4 communicate with one other over the hallle Well 8 and the compartments 6 and 5 lie below the tube sheet Y are separated from one another by the hallie 8. The tube sheets 6 and 'i sup port a 1, number oi water tubes 9 which oller free communication between the compartment and. the coinpertments 5 and 5 The to be cooled enters the cooler through an inlet 10, flows upward through the compartment 3 over the top of the haflle 8 and into compartment 4, thence downwax-rally to an outlet 11 where it leaves the cooler. The path of the gas indicated in the figure by arrows.

Cooling water enters the compartment 5 tin-ough an inlet- 12 through the right hand bank of tubes 9 to the compartment- 2, then down through the left hand bani; of tubes into the compartment 5", from which itflows away through an exit line 13. The flow of cooling Water is preferably so regulated that the level of the water in the coinpartmcnt 2 will be substantially constant, as indicated, for example, by the line 14-.

The entering the cooler is generally at a temperature of about 75 degrees C. and

is reduced therein to a temperature of 28 to 3i) degrees G. As will be noted, the cooler operates on the counter-current system and the temperature of the cooling water ap-- preaches that the gas entering the cooler. As above explained, if temporarily hard waters are used, this causes formation of scale and loss of CO because of the evaporai and steaming of the Water.

in order to prevent the escape of CU and the co; equent formation of scale on the water tubes 9. a layer 15 of oil is placed Water in the compartment and. tnally seals the cooler against 7 of i and. In this the decomposition calcium carbon v carded engine oil or old wash oil from a ben- Z01 extraction plant may be employed.

'Iheoretically, it is only necessary to maintain an unbroken film of oil over the water surface, but in practice it is generally preferable to use a layer of from one-half to three inches in thickness or, in some cases,

even more.

While I have illustrated and described one embodiment of the invention, it. will be understood that it is not thus limited as itmay be otherwise embodied within the scope of the following claims.

I claim:

1. The method of amenting the decomposition of bicarbonates in solution upon heating thereof, which includes covering the solution with a substanially immiscible liquid of low vapor pressure. I

2. ihe method of preventing the decomheating thereof, which includes covering the solution with a layer of substantially immiscible liquid of low vapor pressure, said layer being at least about oneha-lf inch thick.

The method of preventing the decomposition of bicarbonates in solution upon heating thereof which includes covering the solution with a layer of oil from about onehalf inch to about three inches thick.

6. The method of preventing the decomposition of bicarbonates in solution upon heating thereof, which includes covering the solution with a liquid of low vapor pressure, the. liquid being substantially immiscible with the solution.

7. The method of preventing the decomposition of bicarbonates in solution upon heating thereof, which includes maintaining a film of oil on the surface of the solution.

In testimony whereof I have hereunto set my hand.

J 'JSEPH ALLAN SHAIV. 

